A party who intends to raise an issue about a foreign country's law must give notice by a pleading or other writing. In determining foreign law, the court may consider any relevant material or source, including testimony, whether or not submitted by a party or admissible under the Rules of Evidence. The court's determination must be treated as a ruling on a question of law.

Rule 44.1 was amended, effective March 1, 2011, in response to the December 1, 2007, revision of the Federal Rules of Civil Procedure. The language and organization of the rule were changed to make the rule more easily understood and to make style and terminology consistent throughout the rules.